NBSIR 77-1219

Optical Materials

Characterization

Albert Feldman, Deane Horowitz and Roy M. Waxier

Inorganic Materials Division

Institute for Materials Research

and

Marilyn J. Dodge and Warren K. Gladden

Optical Physics Division

Institute for Basic Standards

National Bureau of Standards

Washington, D. C. 20234

March 1977

Semi-Annual Technical Report

Period Covered: August 1 , 1 976 to January 31,1 977

ARPA Order No: 2620

Prepared for Advanced Research Projects Agency

Arlington, Virginia 22209

NBSIR 77-1219

OPTICAL MATERIALS

CHARACTERIZATION

Albert Feldman, Deane Horowitz and Roy M. Waxier

Inorganic Materials Division

Institute for Materials Research

and

Marilyn J. Dodge and Warren K. Gladden

Optical Physics Division

Institute for Basic Standards

National Bureau of Standards

Washington, D. C. 20234

March 1977

Semi-Annual Technical Report

Period Covered: August 1, 1976 to January 31, 1977

ARPA Order No. 2620

Prepared for Advanced Research Projects Agency

Arlington, Virginia 22209

U.S. DEPARTMENT OF COMMERCE, Juanita M. Kreps, Secretary

Dr. Betsy Ancker-Johnson, Assistant Secretary for Science and Technology

NATIONAL BUREAU OF STANDARDS. Ernest Ambler, Acting Director

OPTICAL MATERIALS CHARACTERIZATION

Albert Feldman, Deane Horowitz and Roy M. Waxier

Inorganic Materials Division

Institute for Materials Research

and

Marilyn J. Dodge and Warren K. Gladden

Optical Physics Division

Institute for Basic Standards

ARPA Order No 2620

Program Code Number 4D10

Effective Date of Contract January 1, 1974

Contract Expiration Date December 31, 1977

Principal Investigator Albert Feldman

(301) 921-2840

The views and conclusions contained in this document are those

of the authors and should not be interpreted as necessarily

representing the official policies, either expressed or implied,

of the Advanced Research Projects Agency or the U.S. Government.

OPTICAL MATERIALS CHARACTERIZATION

Abstract

The refractive indices of three prisms of chemical vapor deposited

ZnS were measured at room temperature over the wavelength range 540 nm

to 1.083 pm. The refractive indices of eight specimens of CaF2 doped

with Er were measured from 404.7 nm to 1.083 pm. The doping range was 0.001% to 3% Er. Interferometric measurements of dn/dT were made over

the temperature range -180 °C to 200 °C at the wavelengths 632.8 nm and

3.39 pm on single crystal specimens of BaF 2 , CaF2 , reactive atmosphere

processed (RAP) KBr, RAP KC1, KC1 doped with KI , LiF, NaF and SrF2 , and

on chemical vapor deposited (CVD) ZnSe and hot forged CaF 2

.
'
1

Table of Contents

1. Technical Report Summary 1

1.1 Technical Problem 1

1.2 General Methodology 1

1.3 Technical Results 2

1.4 Department of Defense Implications 3

1.5 Implications for Further Research 3

2. Technical Report 4

2.1 Refractive Index of CVD Zinc Sulfide and ErbiumDoped Calcium Fluoride - Marilyn J. Dodge and

Warren K. Gladden 4

2.1.1 Introduction 4

2.1.2 Experimental Technique 4

2.1.3 Experimental Results 5

2.1.4 Conclusions 5

2.1.5 References 6

2.2 Effect of Temperature on the Refractive Indices of

of Window Materials - Albert Feldman, Deane Horowitz

and Roy M. Waxier 10

2.2.1 Introduction 10

2.2.2 Apparatus 10

2.2.3 Data Analysis 11

2.2.4 Results and Discussion 12

2.2.5 References 12

3. Acknowledgments 30
*
1

OPTICAL MATERIALS CHARACTERIZATION

1. Technical Report Summary

1 . 1 Technical Problem

Windows subjected to high-average-power laser radiation will undergo

optical and mechanical distortion due to absorptive heating. If the

distortion becomes sufficiently severe, the windows become unusable.

Theoretical calculations of optical distortion in laser windows depend

on the following material parameters; absorption coefficient, refractive

index, change of index with temperature, thermal expansion coefficient,

stress-optical constants, elastic compliances, specific heat, thermal

conductivity and density. Our program has been established to measure

refractive indices, changes of index with temperature, stress-optical

constants, elastic compliances, and thermal expansion coefficients of

candidate laser window materials.

1 . 2 General Methodology

Laboratory experiments are conducted for measuring refractive

indices, changes of index with temperature, stress-optical constants,

elastic compliances, and thermal expansion coefficients.

The refractive indices of prismatic specimens are measured on precision spectrometers by using the method of minimum deviation. Two

spectrometers are used. One instrument, which uses glass optics, is

used for measuring refractive indices in the visible with an accuracy of

several parts in 106. The other instrument, which uses mirror optics,

is used for measuring refractive indices in the ultraviolet and the

infrared to an accuracy of several parts in 10 5

. Using both spectrometers we can measure refractive indices over the spectral region 0.2 ym

to 50 ym.

We measure the coefficient of linear thermal expansion, a, by a method of Fizeau interferometry. The interferometer consists of a specially prepared specimen which separates two flat plates. Interference fringes are observed due to reflections from the plate surfaces

in contact with the specimen. We obtain a by measuring the shift of

these interference fringes as a function of temperature. We can measure

a from -180 °C to 800 °C.

The change of refractive index with temperature, dn/dT, is measured

by two methods. In the first method, we measure the refractive index

with the precision spectrometers at two temperatures, 20 °C and 30 °C,

by varying the temperature of the laboratory. This provides us with a measure of dn/dT at room temperature. The second method may be used for
-2

measuring dn/dT from -180 °C to 800 °C. We obtain dn/dT from a knowledge of the expansion coefficient and by measuring the shift of Fizeau

fringes in a heated specimen as a function of temperature. The Fizeau

fringes are due to interferences between reflections from the front and

back surfaces of the specimens.

We measure piezo-optic coefficients and elastic compliances using a combination of Twyman-Green and Fizeau interferometers. From the shift

of fringes in specimens subjected to uniaxial or hydrostatic compression,

we obtain the necessary data for determining all the stress-optical con- stants and elastic compliances.

In materials with small piezo-optic constants or in materials that

cannot withstand large stresses, we use interferometers designed to

measure fractional fringe shifts. At 10.6 ym we use a modified TwymanGreen interferometer which has a sensitivity of 0.01A. At 632.8 nm, we

use a modified Dyson interferometer which has a sensitivity of 0.002A.

When using these interferometers to measure piezo-optic constants we must know the elastic constants of the material under test.

1 . 3 Technical Results

The refractive indices of three specimens of chemical vapor deposited

(CVD) ZnS were measured at room temperature over the wavelength range

540 nm to 1.083 ym. The refractive indices of eight specimens of CaF2 doped with Er were measured from 404.7 nm to 1.083 ym. The doping range was 0.001% to 3% Er. The latter measurements were done at the request

of Dr. Fontanella of the United States Naval Academy.

We have measured the linear thermal expansion and dn/dT of the

following materials:

The measurements were made by Fizeau interferometry over the temperature range from -180 °C to 200 °C. We measured dn/dT at 632.8 nm and

at 3.39 ym. The thermal expansion data were in good agreement with

earlier published data.

In addition to the above measurements on potential laser window

materials, we have measured the linear thermal expansion coefficient and

dn/dT of Plexiglas 55, a material used in the construction of aircraft

windows. This work was done at the request of Captain Hurst of the Air

Force Materials Laboratory at Wright-Patterson Air Force Base.

BaF2

CaF 2 KBr (RAP)*

KC1 (RAP)*

KC1 doped with KI (KC1:KI)

LiF

NaF

SrF2 ZnSe (CVD)

*reactive atmosphere processed.
3

1 . 4 Department of Defense Implications

The Department of Defense is currently constructing high-power

laser systems. Criteria are needed for determining the suitability of

different materials for use as windows in these systems. The measurements we are performing provide data that laser system designers can use

for determining the optical performance of candidate window materials.

1 . 5 Implications for Further Research

Measurements of refractive index, dn/dT, thermal expansion, and

piezo-optical constants will be continued on candidate laser window

materials as well as on other optical materials of interest to the

Department of Defense. We shall continue our efforts on measurements at

3.39 ym, which is within the wavelength range of interest to designers

of chemical laser systems (2-5 ym range)

The wavelengths of primary interest will shift from the infrared to

the ultraviolet. The infrared laser window program is now coming to

completion, whereas, interest is growing for optical materials data in

the ultraviolet because of the development of powerful new lasers in the

ultraviolet. These lasers include the XeF laser operating at 354 nm and

the KrF laser operating at 248 nm. Procurement is proceeding for an argon ion laser and a frequency doubler. The laser will be operated in

the ultraviolet to obtain radiation at 351 nm which is close to the XeF

wavelength. We will double the 514.5 nm line to 258 nm which is near

the KrF wavelength. We will then proceed to measure the optical properties of potential uv laser window materials.

At present, we are searching the literature for optical data on uv materials. Preliminary results indicate that very little dn/dT data

exists and that photoelastic constant data are almost nonexistant in the uv region of the spectrum.
- 4 -

2. Technical Report

2.1

Refractive Index of CVD Zinc Sulfide and Erbium-Doped Calcium

Fluoride

Marilyn J. Dodge and Warren K. Gladden

2.1.1

Introduction

Chemical vapor deposited (CVD) zinc sulfide is a promising candidate

infrared laser window material. It is considered to have an useful

transmission range from about 0.6 to 13ym with a strong absorption band

at 6ym [1], Three samples of thisj material have been submitted by

B. A. de Benedetto of Raytheon Co . The three specimens were identified

as "standard", "high-scatter", and "high-temperature", and for the

purpose of this report the samples will be designated as S, HS and HT

respectively. Preliminary refractive index measurements were made on

the S and HS samples of ZnS from 0.5461 to 1.083ym. The measurement of

index was not possible on the HT sample below 0.78ym because of almost

total absorption, but the refractive index has been determined from

0.7800 to 1.12ym. From visual observations, the S sample exhibited much

more scatter than the HS sample.

Eight specimens of erbium-doped calcium fluoride were made available

by John Fontanella of the U.S. Naval Academy for index of refraction

measurements. The samples were all grown at the Harshaw Chemical Company.

The samples were designated as follows:

CaF :Er.001%, CaF :Er.003%, CaF :Er.01%, CaF :Er.03%, CaF :Er.l%,

CaF2:Er.3%, CaF

2 :Er 1%, and CaF

2 :Er 3%. The refractive index was determined for each sample at II wavelengths from 0.4047ym to 1.083ym.

2.1.2

Experimental Technique

The specimens were in prismatic form and were measured by means of

the minimum-deviation method on a Wild precision spectrometer. The

index was determined at known emission wavelengths of mercury, cadmium

and helium. An infrared image converter was used to facilitate the

measurement of the near IR lines.

1. Figures in brackets indicate the literature references at the end of

this paper.

2. The use of company and brand names in this paper are for identification

purposes only and in no case does it imply recommendation or endorsement

by the National Bureau of Standards and it does not imply that the

materials used in this study are necessarily the best available.
2.1.3 Experimental Results

- 5 -

The refractive index of the standard ZnS sample ranges from 2.3881

at 0.5461ym to 2.2869 at 1.083ym. The index of the h^-scatter sample

was lower than the standard specimen by about 3 x 10 , a^d the hitemperature sample has an index in the near IR of 2 x 10 higher than

the standard sample. The dispersion curve for ZnS is shown in fig. ,L. The experimental index values are considered accurate within 3 x 10

The index of refraction of the Er-doped CaF„ increases with the

increase in percentage of dopant. The index of CaF„:Er.001% is compared

with a recently studied sample of hot-forged CaF^ [2] in Table 1. The

increase in refractive index of each subsequent sample over the one preceding it is also shown in Table 1. As the percent of dopant

increases to greater than .003% the increase in refractive index is

almost predictable. The average chang^ in refractive index over the

wavelength range studied is 2.12 x 10 per 1% increase of erbium.

There appears to be a slightly higher change in the blue than in the

red region of the spectrum. Figure 2 shows index plotted as a function

of wavelength for CaF2:Er.001%, CaF

2 :Er.l%, CaF2 :Er 1% and CaF

2 :Er 3%.

Refractive index values are plotted as a function of percent or erbium

at five wavelengths in_]Iigure 3. These values of refractive index are accurate within 1 x 10

2.1.4 Conclusions

The results discussed in this report are preliminary and for the

visible and near IR regions of the spectrum only and should not be used

in an attempt to predict the behavior of the refractive index in the

infrared region of the spectrum for ZnS or in the IR or UV regions for

CaF

2 :Er. Index determinations are planned for all three samples of the

CVD ZnS out to the IR absorption edge. Representative samplings of the

erbium-doped CaF

2 will be measured from 0.2ym or, the UV absorption edge

if higher than 0.2ym, to the IR limits of transmittance.
2.1.7 References

[1] B. A. de Benedetto, Private communication.

[2] M. J. Dodge, "Laser Induced Damage in Optical Materials: 1976,

P. 64, N.B.S. Special Publication 462, U.S. Govt. Printing

Office, Wash. (1976).
TABLE

I

-

CHANGE

IN

REFRACTIVE

INDEX

OF

CaF„:Er

WITH

INCREASE

IN

PERCENTAGE

OF

Er

7

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Fig. 1 - The refractive index of CVD ZnS as a function of

wavelength. The data points represent the index of a sample

of hi-temperature CVD ZnS.
9

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10 -

2 . 2 Effect of Temperature on the Refractive Indices of Window Materials

Albert Feldman, Deane Horowitz and Roy M. Waxier

2.2.1 Introduction

When high-power radiation propogates through a laser window, the

residual absorption causes a temperature rise in the window. The temperature distribution is, in general, nonuniform and hence, will distort

the wavefront of the beam. The distortion arises from: the change of

refractive index with temperature; the change of thickness with temperature; the change of refractive index and thickness caused by stresses

produced by thermal gradients. If the distortion is sufficiently severe,

the laser window becomes unusable. In order to predict the distortion

of a laser beam wavefront from the laser energy deposited in a window,

one requires certain material parameters. These include the absorption

coefficient, the refractive index n, the change of index with temperature

dn/dT, the piezo-optic constants q-^j , the thermal expansion coefficient

a, and the elastic constants s-jj or c.jj . It is the purpose of the

Optical Materials Characterization Program at the National Bureau of

Standards to measure n, dn/dT, q„ and if necessary, a and s .

In this report, we present data of dn/dT obtained on BaF2 , CaF2 , KBr (RAP), KC1 (RAP), KC1 nominally doped with 1% KI (KC1:KI), LiF, NaF,

SrF2 and ZnSe (CVD). Data were obtained at 632.8 nm and 3.93 ym over

the temperature range -180 °C to 200 °C. The data were obtained by the

method of Fizeau interferometry which requires a knowledge of the thermal

expansion coefficient. We measured the linear thermal expansion coefficients of all the above specimens and found the results to be in good

agreement with published values. We used the published values in our computations

.

In addition, we have measured the linear thermal expansion and

dn/dT over the temperature range -160 °C to 60 °C of Plexiglas 55, a material used for aircraft windows. The measurements were made at the

request of Captain Hurst of the Air Force Materials Laboratory for

determining the effect of heating caused by a nuclear explosion on the

optical properties of aircraft windows.

2.2.2 Apparatus

The thermal expansion and dn/dT were measured by the method of

Fizeau interferometry. The general method for making these measurements

has been described in the literature [1].

To measure thermal expansion, we measure as a function of temperature the shift of Fizeau fringes formed between two optic flats separated

by a specimen. To measure dn/dT, we measure as a function of temperature

the shift of Fizeau fringes formed from the reflections from the front

and back surfaces of a specimen polished plane parallel.
11

We vary the temperature by placing the specimens in a furnace that can be cooled to -180 °C. We then heat the furnace electrically which

permits us to reach all temperatures between -180 °C and 200 °C. The

details of the experimental method were presented in our previous report

[ 1 ].

2.2.3 Data Analysis

The thermal expansion data is obtained in the form of a fringe

count as a function of temperature. The linear thermal expansion coefficient, a, is defined by

( 1 )

where t Q is the room temperature specimen thickness, and t is the specimen thickness at temperature T. In terms of a fringe count N. at a temperature T^ we calculate a(T) by the formula

N.-N

“ <T) - 2T < 2 > O 11-1

where A is the wavelength of the laser used in the experiment and T = (T 1+T^_ 2

) /2. A graph is then made of a as a function of T. On this

graph we also plot either the accepted handbook values of a(T) when they

are available, or else values from the literature. A curve is then

visually drawn through the data and from this curve, we abstract a set

of data points. These points are then fitted by computer to a tenth

degree polynominal. The purpose of the fit is to obtain an analytical

expression for a(T). This expression is needed for computing dn/dT as a function of temperature.

The change of index with temperature is also obtained in the form

of a fringe count at a particular temperature. The change of index

from room temperature to temperature T^ is given by

An(T.

)

l

M. A l At

o t (i + Ai) i

o

(3)

where n is the refractive index at room temperature and At/t Q is computed

at temperature T_^. We obtain dn/dT from

dn(T)

dT

An(T.) - An(T._

1

) T. - T. . l l-l

( 4 )
- 12

The values of dn/dT are then fitted to a third degree polynominal in

temperature and tabulated in 20 °C increments.

2.2.4 Results and Discussion

The linear thermal expansion and dn/dT were measured on specimens

of BaF2 , CaF2 , KBr (RAP), KC1 (RAP), KC1:KI, LiF, NaF, SrF2 and ZnSe

(CVD). All the specimens used were of single crystal material except

for the ZnSe which was polycrystalline. We also made measurements on hot forged CaF2 and these data agreed with the single crystal data.

The values we obtained for the linear thermal expansion agreed well

with values from the literature, hence, they are not presented here.

However, references to the linear thermal expansion are listed in

Table 2, which contains the data used for computing dn/dT.

In figures 4-9

? we plot dn/dT as a function of T for the above

materials. The points in each of the figures are the experimentally

determined values. Through each set of points, we draw a line visually.

This line agrees quite well with a third degree polynominal least squares

fit to the data of dn/dT as a function of temperature. The results of

the fit are tabulated in Tables 3-11. The errors in the tables are the

standard deviation of the experimental data to the least squares fit.

In figure IQ we show plotted the linear thermal expansion coefficient of Plexiglass 53 as a function of temperature. Figure 11 is a plot

of dn/dT of Plexiglass 55 as a function of temperature.

In a recent article, R. J. Harris, et al. [2] presented dn/dT data

on a series of materials including BaF2 , CaF 2 , KC1, and ZnSe. At first

glance, there appears to be some disagreement between their data and

ours; however, if we correct their results by using our values for n and

a, we find good agreement in the data for BaF2 , CaF 2 , and KC1. There

still remains a discrepancy between our values for ZnSe and theirs. We are in the process of measuring dn/dT of ZnSe at 632.8 nm using an immersion technique similar to the technique used by Harris, et al . in

order to further compare our data.

2.2.5 References

[1] A. Feldman, D. Horowitz, R. M. Waxier, and M. J. Dodge, Optical

Materials Characterization , National Bureau of Standards Internal

Report, NBSIR 76-1115 (Aug. 1976).

[2] R. J. Harris, G. T. Johnston, G. A. Kepple, P. C. Krok, and H. Mukai,

Appl. Optics 16, 436 (1977).
- 13-

Table 2. Data Used in Computation of dn/dT

Material Refractive

632.8 nm

Index, n

o 3.39 pm

t o (mm)

a

BaF

2 1.473

a 1.460

a 13.16 b

CaF

2 1.433

C 1. 416C 13.41 b, d,e,f

KBr(RAP) 1.557 S 1.536 s 11.83 h

KCl(RAP) 1.488j 1.473^ 11.87 h

KC1 : KI 1.488 j 1.473^ 6.11 h

LiF 1.392

k

1.360

k

5.59 h

NaF 1.325

1

1.312

1 12.21 h

SrF

2 1 . 436

m

1.425

n 13.15 b

ZnSe(CVD) 2. 590P

2 . 436P 17.49 q>r

I.H. Malitson , J. Opt. Soc.

k

A.C. Bailey & B. Yates , Proc. Phys

.

Amer. 54, 628 (1964). Soc. 91, 390 (1967) •

C

I.H. Malitson , Appl. Opt. 2, ^D.N. Batchelder & R .0. Simmons;, J.

1103 (1963). Chem. Phys. 41, 2324 (1964).

6

S.S. Sharma, Proc. Indian Acad. ^S. Valentiner & J. Wallot, Annl. Phys . , Sci. A31 , 261 (1950)

.

Lpz 46, 837 (1915).

S R.E. Stephens , E.K. Plyler, R.K. Kirby, T. A. Hahn, & B.D. Rothrock,

W.S. Rodney & R.J. Spindler, American Institute of Physics Handbook

J. Opt. Soc. Amer. 43, 111 Dwight E. Gray ed. (McGraw-Hill Book

(1953)

.

Co. , 1972) pp 4-119 to 4-142.

J A. Feldman, D . Horowitz, R.M. ^.W. Tilton & E.K. Plyler, J. Res. NBS

Waxier, I.H. Malitson & M.J. 47, 25 (1951).

Dodge, Optical Materials

Characterization, NBSIR 76-1010

(Feb. 1976).

1 S.S. Ballard, J.S. Browder & ^.C. Stockbarger, OSRD Report No. 4690

J.F. Ebersole , in American Dec. 31, 1944.

Institute of Physics Handbook , Dwight E. Gray Ed. (McGrawHill Book Co., 1972) pp. 6-12

to 6-57.

nEstimated ^A. Feldman, D. Horowitz, R.M. Waxier,

I.H. Malitson & M.J. Dodge, Optical

Materials Characterization , NBSIR 75-781

(Aug. 1975).

^J.S. Browder & S.S. Ballard, r Reference [1].

Appl. Optics 8, 793 (1969).
14 -

Table 3 . dn/dT of BaF

2 (10 V1

)

Temperature

Wavelength (ym)

(°c)

0.6328a 3.39

b

-180 - .86 - .81

-160 - .98 - .95

-140 -1.09 -1.07

-120 -1.19 -1.17

-100 -1.27 -1.26

- 80 -1.35 -1.34

- 60 -1.41 -1.41

- 40 -1.47 -1.47

- 20 -1.52 -1.51

0 -1.56 -1.56

20 -1.60 -1.59

40 -1.63 -1.62

60 -1 .'66 -1.66

80 -1.70 -1.68

100 -1.73 -1.71

120 -1.76 -1.75

140 -1.79 -1.78

160 -1.83 -1.82

180 -1.87 -1.87

200 -1.92 -1.92

Standard deviation from a third degree polynomial fit is

^Standard deviation from a third degree polynomial fit is
- 15

Table 4. dn/dT of CaF

2 (10"V1

)

Temperature

Wavelength (ym)

(°c)

0.6328 a 3.39

b

-180 - .40 - .40

-160 - .54 - .52

-140 - .66 - .63

-120 - .77 - .73

-100 - .85 - .82

- 80 - .93 - .89

- 60 - .99 - .95

- 40 -1.03 -1.00

- 20 -1.07 -1.05

0 -1.10 -1.09

20 -1.13 -1.12

40 -1.15 -1.14

60 -1.17 -1.17

80 -1.19 -1.19

100 -1.21 -1.21

120 -1.23 -1.23

140 -1.26 -1.25

160 -1.30 -1.27

180 -1.34 -1.30

200 -1.40 -1.34

Standard deviation from a third degree polynomial fit is

^Standard deviation from a third degree polynomial fit is
-16

Table 5 . dn/dT of KBr (10

5 K

1

)

Temperature

Wavelength (pm)

(°C)

0.6328a 3.39

b

-180 -2.95 -3.05

-160 -3.17 -3.26

-140 -3.36 -3.44

-120 -3.53 -3.60

-100 -3.67 -3.74

- 80 -3.78 -3.85

- 60 -3.88 -3.95

- 40 -3.96 -4.03

- 20 -4.02 -4.10

0 -4.08 -4.16

20 -4.12 -4.21

40 -4.16 -4.25

60 -4.19 -4.29

80 -4.23 -4.33

100 -4.27 -4.36

120 -4.31 -4.40

140 -4.36 -4.44

160 -4.42 -4.49

180 -4.49 -4.55

200 -4.58 -4.62

Standard deviation from a third degree polynomial fit is .03

^Standard deviation from a third degree polynomial fit is .03
17

Table 6. dn/dT of KC1 (10

5 K

1

)

Temperature

Wavelength (ym)

(°C)

0.6328 a

3. 39

b

-180 -2.32 -2.39

-160 -2.52 -2.58

-140 -2.70 -2.75

-120 -2.86 -2.91

-100 -3.00 -3.05

- 80 -3.13 -3.17

- 60 -3.24 -3.28

- 40 -3.35 -3.38

- 20 -3.43 -3.47

0 -3.51 -3.55

20 -3.58 -3.62

40 -3.65 -3.69

60 -3.70 -3.75

80 -3.76 -3.80

100

i

—

1

1 CO 00 -3.85

120 -3.86 -3.90

140 -3.91 -3.94

160 -3.96 -3.99

180 -4.02 i o 200 -4.08 -4.09

3. Standard deviation from a third degree polynomial fit is .02

^Standard deviation from a third degree polynomial fit is .02
18 -

Table 7. dn/dT of KC1:KI (10

5 K1

)

Temperature

Wavelength (ym)

(°C)

0.6328a 3.39

b

-180 -2.33 -2.44

-160 -2.53 -2.61

-140 -2.70 -2.77

-120 -2.86 -2.92

-100 -3.00 -3.05

- 80 -3.13 -3.17

- 60 -3.24 -3.28

- 40 -3.35 -3.38

- 20 -3.44 -3.47

0 -3.52 -3.55

20 -3.59 -3.63

40 -3.66 -3.69

60 -3.72 -3.75

80 -3.77 -3.81

100 -3.82 -3.86

120 -3.87 -3.92

140 -3.92 -3.97

160 -3.96 -4.01

180 -4.01 -4.06

200 -4.07 -4.11

Standard deviation from a third degree polynomial fit is .02

^Standard deviation from a third degree polynomial fit is .03
- 19

Table 8. dn/dT of LiF (10

5 K1

)

Temperature

Wavelength (ym)

(°C)

0.6328a 3.39

b

-180 - .36 - .40

-160 - .63 - .60

-140 - .86 - .78

-120 -1.05 - .93

-100 -1.21 -1.06

- 80 -1.34 -1.16

- 60 -1.44 -1.25

- 40 -1.52 -1.32

- 20 -1.59 -1.37

0 -1.63 -1.42

20 -1.67 -1.45

40 -1.70 -1.48

60 -1.72 -1.51

80 -1.75 -1.53

100 -1. 78 -1.56

120 -1.81 -1.59

140 -1.85 -1.63

160 -1.91 -1.67

180 -1.99 -1.73

200 -2.09 -1.80

Standard deviation from a third degree polynomial fit is .02

^Standard deviation from a third degree polynomial fit is .04
- 20

Table 9. dn/dT of NaF (10

5 R1

)

Temperature

Wavelength (ym)

(°c)

0.6328 a 3.39

b

-180 - .51 - .55

-160 - .67 - .69

-140 - .81 - .82

-120 - .92 - .92

-100 -1.00 -1.00

- 80 -1.07 -1.06

- 60 -1.12 -1.11

- 40 -1.16 -1.14

- 20 ON I1—

i 1 !— -1.17

0 CM o

i 1 1— -1.18

20 -1.21 -1.19

40 -1.21 -1.19

60 ‘-1.22 -1.19

80 -1.22 -1.20

100 -1.22 -1.20

120 -1.24 -1.21

140 -1.26 -1.23

160 -1.29 -1.26

180 -1.33 -1.30

200 -1.39 -1.35

Standard deviation from a third degree polynomial fit is .05

^Standard deviation from a third degree polynomial fit is .05
- 21

Table 1 GL dn/dT of SrF

^ (10

' 5 k

1

)

Wavelength (ym)

Temperature

(°c)

0 . 6328 a

3 . 39

b

-180 - .56 - .56

-160 - .69 - .68

-140 - .81 - .80

-120 - .90 - .89

-100 - .98 - .97

- 80 - 1.05 - 1.04

- 60 - 1.11 - 1.10

- 40 - 1.15 - 1.15

- 20 - 1.19 - 1.19

0 - 1.22 - 1.22

20 - 1.24 - 1.24

40 - 1.25 - 1.26

60 -1.27 - 1.27

80 -1.28 - 1.28

100 - 1.29 - 1.29

120 - 1.30 - 1.29

140 - 1.32 - 1.30

160 - 1.34 - 1.31

180 - 1.36 - 1.32

200 -1.39 - 1.33

Standard deviation from a third degree polynomial fit is

^Standard deviation from a third degree polynomial fit is
22

Table 1L dn/dT of ZnSe (10 V1

)

Temperature

Wavelength (ym)

(°c)

0.6328a 3.39

b

-180 7.6 5.0

-160 8.2 5.2

-140 8.7 5.4

-120 9.1 5.6

-100 9.4 5.8

- 80 9.7 5.9

- 60 10.0 6.0

- 40 10.2 6.1

- 20 10.3 6.1

0 10.5 6.2

20 10.6 6.2

40 10.7 6.2

60 10.8 6.3

80 10.9 6.3

100 11.0 6.3

120 11.1 6.4

140 11.3 6.4

160 11.5 6.5

180 11.8 6.6

200 12.1 6.7

Standard deviation from a third degree polynomial fit is

Standard deviation from a third degree polynomial fit is .1
CNJ

(i>i 9.m)ip/up

Figure

4.

dn/dT

of

CaF„

and

BaF
-200 -100 0 100 200

TEMPERATURE (°C)

Figure 5. dn/dT of KC1 (RAP), KBr (RAP)

and KC1 doped with KI (KC1:KI).
CM

CM

TEMPERATURE

(°C)
(

• r

( »

s

.0l) ip/up

I

I I

TEMPERATURE

(°C)
(,.^.01) lp/up

TEMPERATURE

(°C)
12

-200 -100 0 100 200

TEMPERATURE (°C)

Figure 9. dn/dT of ZnSe (CVD)

.
LOm

3 cfi o 03 *H t—

4

c/3 bo 3 -H

03 X a a) X rH

ai eu

c

0) •HO

3-i -H

03 4-1 a; u-i 3 ai •h o J o

cu

4/3

bO

•H

P4

-E 0! 4J 3-i (V a -w O *H

3-

i t-H

4-

1

c/3 OJ -

3-1 3-1 03 Q)

3-i cn 3

<D 4-1 r—t G

bO OJ 3 lw

03 3

•H c

S-i 03 h a

(|-X9

-0I) o
(,-Xg-OI) IP/UP

-160

-80

0

80

160

TEMPERATURE

(°C)
-31

3. Acknowledgments

We thank Dr. Phillip Klein of the Naval Research Laboratory for

supplying the RAP KC1 and RAP KBr. We thank Dr. Bernal of Honeywell for

supplying the KC1 doped with KI. The CVD ZnS was supplied by Raytheon.

CVD ZnSe was provided both by Dr. Perry Miles of Raytheon and Dr. Carl Pitha

of RADC. Polycrystalline CaF2 was supplied by R. J. Harris of the

University of Dayton Research Institute.

<%
NBS-1 14A (REV. 7-73)

U.S. DEPT. OF COMM.

BIBLIOGRAPHIC DATA

SHEET

1. PUBLICATION OK REPORT NO.

NBSIR 77-1219

2. Gov't Accession

No.

3. Recipient’s Accession No.

4. TITLE AND SUBTITLE

Optical Materials Characterization

5. Publication Date March 1977

6. Performing Organization Code

7. AUTHOR(S)

Albert Feldman, Deane Horowitz, Roy M. Waxier, Marilyn J. Pod

8 . Performing Organ. Report No.

;e

9. PERFORMING ORGANIZATION NAME AND ADDRESS

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

10. Project/Task/Work Unit No. 3130442

11. Contract/Grant No.

12. Sponsoring Organization Name and Complete Address (Street, City, State, ZIP)

Advanced Research Projects Agency

Arlington, Virginia 22209

13. Type of Report & Period

Covered , Semi-Annual

14. Sponsoring Agency Code

15. SUPPLEMENTARY NOTES

16. ABSTRACT (A 200-word or less factual summary of most significant information. If document includes a significant

bibliography or literature survey, mention it here.)

The refractive indices of three prisms of chemical vapor deposited ZnS were measured at room temperature over the wavelength range 540 nm to 1.083 ym. The

refractive indices of eight specimens of CaF2 doped with Er were measured from

404.7 nm to 1.083 ym. The doping range was 0.001% to 3% Er. Interferometric

measurements of dn/dT were made over the temperature range -180 °C to 200 °C at

the wavelengths 632.8 nm and 3.39 ym on single crystal specimens of BaF 2 , CaF 2 , reactive atmosphere processed (RAP) KBr , RAP KC1, KC1 doped with KI, LiF, NaF

and SrF2 , and on chemical vapor deposited (CVD) ZnSe and hot forged CaF 2

.

17. KEY WORDS (six to twelve entries; alphabetical order; capitalize only the first letter of the first key word unless a proper name; separated by semicolons)

BaF 9 ; CaF ?

; KBr; KC1 ; LiF; NaF; refractive index; SrF? ; thermal coefficient

of refractive index; ZnSe.

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